Control circuit, switching power supply circuit, and control method

Abstract

Disclosed are a control circuit of a power converter and a control method thereof, a switching power supply circuit and a driving control method. The control circuit comprises: a sampling unit configured to sample an input voltage, an output voltage and an output current of the power converter to obtain a plurality of sampling signals; a valley bottom locking controller electrically connected to the sampling unit and configured to adaptively select a most suitable valley bottom matching a current input-output specification according to the plurality of sampling signals; and a driving controller configured to turn on a power tube at the most suitable valley bottom after demagnetization of the power converter ends. The present disclosure provides a new quasi-resonant control technology, which can realize valley bottom locking and adaptive adjustment for each input-output specification, thereby avoiding the phenomenon of "jumping valley bottom" while adapting to multiple input-output specifications, and improving the efficiency and electromagnetic interference resistance performance.

Description

Technical Field

[0001] This disclosure relates to power electronics technology, and in particular to control circuits and control methods for power converters, switching power supply circuits, and drive control methods. Background Technology

[0002] Switching power supplies offer advantages such as ease of control, high efficiency, small size, and high reliability, and are widely used in devices such as television power supplies, mobile phone chargers, LEDs, industrial instruments, and power adapters. Increasing the switching frequency of power switching devices in switching power supplies can bring many beneficial effects, such as reducing audio noise, improving dynamic response speed, and reducing circuit size and weight. Therefore, increasing the switching frequency is an important direction for the development of switching power supply technology. However, because the power switching devices in switching power supplies are not ideal switching devices, increasing the switching frequency leads to greater switching losses.

[0003] To achieve higher operating frequencies while reducing switching losses, quasi-resonant control technology can be employed. A switching power supply operating in quasi-resonant mode turns on the power switching device when it detects zero or low voltage across the device, thereby reducing switching losses. Furthermore, quasi-resonant control technology also helps to weaken electromagnetic interference (EMI) signals.

[0004] Taking a flyback-type switching power supply as an example, traditional quasi-resonant control techniques typically set a shielding time T. blk Valley bottom detection window time T w Among them, the shielding time T blk It can be set to a fixed value, starting from the turn-on time of the power transistor on the primary side, with a shielding time T. blk The end time corresponds to the valley detection window time T. w The initial moment, the valley detection window time T w The end time can correspond to the next shielding time T. blk The starting moment.

[0005] The drive controller provides switching control signals to the power transistor, thereby controlling its on and off states. When the power transistor is turned on, the input voltage of the switching power supply magnetizes the transformer's magnetizing inductance and stores energy in the transformer. When the power transistor is turned off, the input voltage of the switching power supply no longer magnetizes the transformer, and the energy stored in the transformer is transferred to the output capacitor to compensate for voltage drops in the output capacitor. After the energy in the transformer is completely released, an oscillating voltage appears at the drain of the power transistor, meaning that the drain-source voltage of the power transistor can exhibit peaks and troughs.

[0006] During the shielding time T blk Within this timeframe, the drive controller is not allowed to turn the power transistor back on. And during the detection window time T at each valley... w Internally, the drive controller detects the drain-source voltage V of the power transistor. ds So that the drain-source voltage V can be detected for the first time within the valley detection window time. ds When the oscillation reaches its trough or afterward, the power transistor is turned on, thus initiating the next conduction phase and the next shielding time T of the power transistor. blk .

[0007] However, while the aforementioned traditional quasi-resonant control technique can achieve valley-level conduction, changes in the output power of the switching power supply or other parameters can alter the rate at which the transformer consumes energy after the power transistor is turned off, causing a shift in the timing of the drain-source voltage oscillation. If the shielding time T... blk If it is a fixed value, the drain-source voltage may vary during the shielding time T. blk Detection window time T at the bottom or at the bottom w When the switching power supply begins to oscillate, the drive controller may turn on the power transistor at different valleys after the oscillation begins. Therefore, valley "locking" cannot be achieved. That is, for any output power, the drive controller cannot guarantee that the power transistor will always be turned on at the x-th valley after the oscillation begins (x is a fixed value and a natural number greater than 0). Even in the steady state of the switching power supply, the turn-on time of the power transistor may periodically switch back and forth between adjacent valleys. Since there is a resonant period interval between adjacent valleys, this defect may cause a large change in the switching period (i.e., the "valley jumping" phenomenon), resulting in unstable switching frequency and poor electromagnetic interference resistance of the switching power supply. Especially in applications such as fast charging products for mobile phones, if the switching power supply uses traditional quasi-resonant technology without "locking" the valley, operating the mobile phone while it is charging can easily cause the "ghost hand" phenomenon on the phone screen (i.e., clicks or swipes that the user cannot control and do not want).

[0008] Therefore, it is hoped that the quasi-resonant control technology of switching power supplies can be optimized to achieve valley locking. Summary of the Invention

[0009] In view of this, the purpose of this invention is to provide a new quasi-resonant control technology that can achieve valley locking and adaptive adjustment of various input and output specifications, thereby avoiding the "valley jumping" phenomenon while adapting to a variety of input and output specifications, and improving efficiency and electromagnetic interference resistance.

[0010] In a first aspect, this disclosure provides a control circuit for a power converter, comprising: a sampling unit for sampling the input voltage, output voltage, and output current of the power converter to obtain multiple sampling signals; a valley-locking controller electrically connected to the sampling unit and adaptively selecting the most suitable valley that matches the current input and output specifications based on the multiple sampling signals; and a drive controller electrically connected to the valley-locking controller to obtain the most suitable valley, so as to turn on the power transistor of the power converter at the most suitable valley after the power converter has finished demagnetizing.

[0011] In some preferred embodiments, the valley bottom locking controller determines the corresponding adapted valley bottom number N based on the values ​​of the plurality of sampled signals. f The optimal valley is characterized by its matching valley number, N. f It is a natural number greater than 0.

[0012] In some preferred embodiments, the valley-locking controller includes: a function construction unit for constructing a down-frequency function based on one or more of the plurality of sampled signals, wherein the independent variable of the down-frequency function corresponds to one of the plurality of sampled signals, and the dependent variable corresponds to an adaptation switching period that is beneficial to the efficiency of the power converter; and an adaptation unit for determining the adaptation switching period based on the values ​​of the sampled signals corresponding to the down-frequency function and its independent variables, and determining the corresponding adaptation valley number N based on the adaptation switching period. f So that the duration of the adapter switch cycle is limited to the Nth cycle. f The switching cycle corresponding to the Nth valley is related to the Nth valley. f Between ±1 valleys corresponding to the switching cycles.

[0013] In some preferred embodiments, the function construction unit establishes the frequency reduction function based on the sampled signal characterizing the output voltage and the sampled signal characterizing the input voltage, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal characterizing the output current, and the adaptation unit substitutes the value of the sampled signal characterizing the output current into the frequency reduction function to determine the adaptation switching period and the adaptation valley number.

[0014] In some preferred embodiments, the function construction unit establishes the frequency reduction function based on the sampled signal characterizing the input voltage and the sampled signal characterizing the output current, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal characterizing the output voltage, and the adaptation unit substitutes the value of the sampled signal characterizing the output voltage into the frequency reduction function to determine the adaptation switching period and the adaptation valley number.

[0015] In some preferred embodiments, the function construction unit establishes the frequency reduction function based on the sampled signal characterizing the output voltage and the sampled signal characterizing the output current, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal characterizing the input voltage, and the adaptation unit substitutes the value of the sampled signal characterizing the input voltage into the frequency reduction function to determine the adaptation switching period and the adaptation valley number.

[0016] In some preferred embodiments, the adapter unit is adapted to: determine the switching period corresponding to each valley based on the inductance value of the primary coil of the transformer in the power converter, the turns ratio between the primary and secondary coils of the transformer, the input voltage, the output voltage, the peak current flowing through the power transistor, and the resonant period after demagnetization.

[0017] In some preferred embodiments, the valley bottom locking controller is also adapted to: adjust the corresponding adaptive valley bottom number according to the values ​​of the plurality of sampled signals in a steady state.

[0018] In some preferred embodiments, the sampling unit includes: an input voltage sampling module for obtaining a sampling signal characterizing the input voltage; an output voltage sampling module for obtaining a sampling signal characterizing the output voltage; and an output current sampling module for obtaining a sampling signal characterizing the output current.

[0019] In some preferred embodiments, the control circuit further includes an auxiliary coil coupled to the primary coil of the transformer in the power converter, and the sampling unit further includes a first voltage divider structure for dividing the voltage across the auxiliary coil to obtain an auxiliary voltage divider signal, so that one or more of the input voltage sampling module, the output voltage sampling module, and the output current sampling module can obtain the corresponding sampling signal based on the auxiliary voltage divider signal.

[0020] In some preferred embodiments, the input voltage sampling module is adapted to sample the auxiliary voltage divider signal during the conduction phase of the power transistor to obtain a sampling signal characterizing the input voltage.

[0021] In some preferred embodiments, the output voltage sampling module is adapted to: sample and hold the auxiliary voltage divider signal at the end of demagnetization to obtain a sampled signal characterizing the output voltage.

[0022] In some preferred embodiments, the output current sampling module is adapted to: obtain the demagnetization duty cycle of the demagnetization time relative to the switching cycle based on the auxiliary voltage divider signal, and obtain a sampling signal characterizing the output current by multiplying the demagnetization duty cycle and the peak voltage sampling value of the transformer primary current sampling resistor.

[0023] In some preferred embodiments, the sampling signal characterizing the output current is selected from one of the following: the product of the demagnetization duty cycle and the peak voltage sampling value of the transformer primary current sampling resistor, the product of the product result and a preset coefficient; or the filtered result obtained by low-pass filtering the product result signal, the product of the filtered result and a preset coefficient.

[0024] In some preferred embodiments, the preset coefficient is proportional to the turns ratio between the primary and secondary coils in the transformer and inversely proportional to the resistance value of the primary current sampling resistor of the transformer.

[0025] In some preferred embodiments, the output current sampling module includes: a voltage peak sampling and holding circuit for a transformer primary current sampling resistor, which performs peak sampling on the voltage at the connection node between the power transistor and the transformer primary current sampling resistor to obtain the peak sampling voltage; a demagnetizing duty cycle extraction circuit, which obtains the demagnetizing time based on the auxiliary voltage divider signal and obtains the demagnetizing duty cycle based on the ratio of the demagnetizing time to the switching cycle; a multiplier, which calculates the product of the demagnetizing duty cycle and the peak sampling voltage to output the product result signal; and an output circuit, which provides a sampling signal characterizing the output current based on the product result signal.

[0026] In some preferred embodiments, the input voltage sampling module is adapted to: divide the voltage across the secondary coil of the transformer to obtain a secondary voltage divider signal, and sample the secondary voltage divider signal during the conduction phase of the power transistor to obtain a sampling signal characterizing the input voltage.

[0027] In some preferred embodiments, the output voltage sampling module includes a second voltage divider structure that divides the output voltage to obtain a sampling signal characterizing the output voltage.

[0028] In some preferred embodiments, the output current sampling module includes a second sampling resistor, the output current of the power converter flows sequentially through a load connected in series and the second sampling resistor, and a sampling signal characterizing the output current is provided at the connection node between the second sampling resistor and the load.

[0029] Secondly, this disclosure provides a control method for a power converter, comprising: sampling the input voltage, output voltage, and output current of the power converter to obtain multiple sampling signals; adaptively selecting the optimal valley that matches the current input and output specifications based on the multiple sampling signals; and turning on the power transistor of the power converter at the optimal valley after the power converter has finished demagnetizing.

[0030] In some preferred embodiments, the step of adaptively selecting the best-fit valley that matches the current input / output specifications based on the plurality of sampled signals includes: determining the corresponding valley number N based on the values ​​of the plurality of sampled signals. f The optimal valley is characterized by its matching valley number, N. f It is a natural number greater than 0.

[0031] In some preferred embodiments, the corresponding adaptation valley number N is determined based on the values ​​of the plurality of sampled signals. f The steps include: constructing a down-frequency function based on one or more of the plurality of sampled signals, wherein the independent variable of the down-frequency function corresponds to one of the plurality of sampled signals, and the dependent variable corresponds to an adaptation switching period that is beneficial to the efficiency of the power converter; and determining the adaptation switching period based on the values ​​of the sampled signals corresponding to the down-frequency function and its independent variable, and determining the corresponding adaptation valley number N based on the adaptation switching period. f So that the duration of the adapter switch cycle is limited to the Nth cycle. f The switching cycle corresponding to the Nth valley is related to the Nth valley. f Between ±1 valleys corresponding to the switching cycles.

[0032] In some preferred embodiments, the step of constructing a down-frequency function based on one or more of the plurality of sampled signals includes: establishing the down-frequency function according to the sampled signal characterizing the output voltage and the sampled signal characterizing the input voltage, wherein the independent variable of the down-frequency function corresponds to the value of the sampled signal of the output current, and the value of the sampled signal of the output current is used to substitute into the down-frequency function to determine the adaptation switching period and the adaptation valley number.

[0033] In some preferred embodiments, the step of constructing a down-frequency function based on one or more of the plurality of sampled signals includes: establishing the down-frequency function according to the sampled signal characterizing the input voltage and the sampled signal characterizing the output current, wherein the independent variable of the down-frequency function corresponds to the value of the sampled signal of the output voltage, and the value of the sampled signal of the output voltage is used to substitute into the down-frequency function to determine the adaptation switching period and the adaptation valley number.

[0034] In some preferred embodiments, the step of constructing a down-frequency function based on one or more of the plurality of sampled signals includes: establishing the down-frequency function according to the sampled signal characterizing the output voltage and the sampled signal characterizing the output current, wherein the independent variable of the down-frequency function corresponds to the value of the sampled signal of the input voltage, and the value of the sampled signal of the input voltage is used to substitute into the down-frequency function to determine the adaptation switching period and the adaptation valley number.

[0035] In some preferred embodiments, the step of determining the adaptive switching period based on the value of the sampled signal corresponding to the frequency reduction function and its independent variable includes: determining the switching period corresponding to each valley based on the inductance value of the primary coil of the transformer in the power converter, the turns ratio between the primary and secondary coils of the transformer, the input voltage, the output voltage, the peak current flowing through the power transistor, and the resonant period after demagnetization.

[0036] In some preferred embodiments, the corresponding adaptation valley number N is determined based on the values ​​of the plurality of sampled signals. f The steps also include: adjusting the corresponding valley number according to the values ​​of the plurality of sampled signals under steady state.

[0037] In some preferred embodiments, the step of sampling the input voltage, output voltage, and output current of the power converter includes: obtaining an auxiliary voltage divider signal based on the voltage across an auxiliary coil coupled to the primary coil of the transformer in the power converter; sampling the auxiliary voltage divider signal during the conduction phase of the power transistor to obtain a sampling signal characterizing the input voltage; sampling and holding the auxiliary voltage divider signal at the end of demagnetization to obtain a sampling signal characterizing the output voltage; obtaining the demagnetization duty cycle of the demagnetization time relative to the switching cycle based on the auxiliary voltage divider signal, and multiplying the demagnetization duty cycle by the peak voltage sampling value of the transformer primary current sampling resistor to obtain a sampling signal characterizing the output current.

[0038] In some preferred embodiments, the sampling signal characterizing the output current is selected from one of the following: the product of the demagnetization duty cycle and the peak voltage sampling value of the transformer primary current sampling resistor, the product of the product result and a preset coefficient; or the filtered result obtained by low-pass filtering the product result signal, the product of the filtered result and a preset coefficient.

[0039] In some preferred embodiments, the preset coefficient is proportional to the turns ratio between the primary and secondary coils in the transformer and inversely proportional to the resistance value of the primary current sampling resistor of the transformer.

[0040] In some preferred embodiments, the step of sampling the input voltage, output voltage, and output current of the power converter includes: dividing the voltage across the secondary coil of the transformer to obtain a secondary voltage divider signal, and sampling the secondary voltage divider signal during the conduction phase of the power transistor to obtain a sampling signal characterizing the input voltage; dividing the output voltage to obtain a sampling signal characterizing the output voltage; and using a second sampling resistor connected in series with the load, using the signal provided at the connection point between the second sampling resistor and the load to characterize the sampling signal of the output current.

[0041] Thirdly, this disclosure also provides a switching power supply circuit, including a rectifier bridge, a power converter, and a control circuit. The rectifier bridge rectifies an AC input signal to generate an input voltage, so that the power converter converts the input voltage to generate an output voltage and an output current acting on a load. The control circuit includes: a sampling unit for sampling the input voltage, the output voltage, and the output current to obtain multiple sampling signals; a valley-locking controller electrically connected to the sampling unit and adaptively selecting the most suitable valley matching the current input and output specifications based on the multiple sampling signals; and a drive controller electrically connected to the valley-locking controller to obtain the most suitable valley, so as to turn on the power transistor of the power converter at the most suitable valley after the power converter demagnetizes.

[0042] Fourthly, this disclosure also provides a drive control method that provides output voltage and output current to a load based on input voltage by controlling the on and off of a power transistor in a power converter. The drive control method includes: sampling the input voltage, the output voltage, and the output current to obtain multiple sampling signals; adaptively selecting the optimal valley that matches the current input and output specifications based on the multiple sampling signals; and turning on the power transistor at the optimal valley after the power converter has finished demagnetizing.

[0043] The power converter control circuit and control method, switching power supply circuit and drive control method provided in this disclosure can adaptively select the valley that best matches the current input and output specifications based on the sampling signals characterizing the input voltage, output voltage and output current, and then turn on the power transistor at the best matching valley. Thus, regardless of whether the output power is in the rising or falling phase, the same input and output specifications correspond to the same switching frequency. This achieves adaptation and valley locking for multiple input and output specifications. While reducing switching power consumption by using quasi-resonant control technology, it also improves efficiency, avoids the "valley jumping" phenomenon, and reduces the impact of electromagnetic interference. Attached Figure Description

[0044] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0045] Figure 1 This shows the terminal voltage V across the power transistor in a flyback switching power supply circuit employing conventional quasi-resonant control technology. ds A schematic diagram of the waveform as a function of time t;

[0046] Figure 2 This diagram shows a schematic diagram of a switching power supply circuit according to an embodiment of the present disclosure;

[0047] Figure 3 This diagram illustrates a structural schematic of a sampling unit and a valley bottom locking controller according to an embodiment of the present disclosure.

[0048] Figure 4 This diagram illustrates the waveform of the auxiliary voltage divider signal changing over time in an embodiment of this disclosure.

[0049] Figure 5 This diagram illustrates the structure of an exemplary output current sampling module 220 according to an embodiment of the present disclosure.

[0050] Figures 6a to 6c Schematic structural block diagrams of valley bottom locking controllers according to embodiments of the present disclosure are shown respectively;

[0051] Figure 7 This diagram illustrates the curves of the adaptive switching frequency versus output current calculated by the function construction unit of this embodiment under different input and output voltages.

[0052] Figure 8 A schematic diagram showing the switching frequency and the adaptive switching frequency of the switching power supply circuit according to an embodiment of the present disclosure as a function of output current is provided.

[0053] Figure 9 This diagram illustrates yet another structural schematic of the sampling unit and valley locking controller according to an embodiment of the present disclosure. Detailed Implementation

[0054] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0055] Unless otherwise specified, the terms “off time”, “on time”, “switching cycle”, “shielding time”, and “valley detection window time” used in this disclosure refer to the corresponding stages and their corresponding time lengths.

[0056] In the description of this disclosure, the symbol for each coil can also represent the inductance value of that coil. For example, the inductance value of the primary coil Lp is represented as Lp in the formula, the inductance value of the secondary coil Ls is represented as Ls in the formula, and the inductance value of the auxiliary coil La is represented as La in the formula. Similarly, the symbol for each resistor can also represent the resistance value of that resistor. For example, the first sampling resistor R... cs1 The resistance value is expressed as R in the formula. cs1 .

[0057] In the description of this disclosure, "sampling" generally refers to the process of obtaining a sampled signal used to characterize a signal. For example, it can refer to the process of sampling analog signal values ​​according to a timing sequence, the process of obtaining signal values ​​characterizing an analog signal using passive devices, the process of obtaining the peak value of an analog signal, and so on. Those skilled in the art can determine the process referred to by "sampling" based on the description of this disclosure without affecting the understanding of the present invention.

[0058] The embodiments disclosed herein are applicable to various types of isolated switching power supply circuits (e.g., using transformers including primary and secondary coils), and their architectures include, but are not limited to, switching power supply circuits with flyback architectures.

[0059] Below are some explanations of terms.

[0060] A flyback switching power supply circuit refers to a circuit where, when the power transistor is turned on (i.e., the primary coil of the transformer is energized by a DC voltage), the transformer acts as an inductor to convert electrical energy into magnetic energy, thereby storing energy. When the power transistor is turned off, the transformer converts magnetic energy into electrical energy, thereby releasing energy. The secondary coil of the transformer does not provide power output to the load during the power transistor's on-state, but only after the power transistor is turned off (i.e., after the DC voltage energization to the primary coil of the transformer stops), does the secondary coil provide power output to the load.

[0061] Demagnetization: This refers to the process by which the transformer's magnetic core returns to a magnetically neutral state, i.e., the process of resetting the transformer's magnetic flux. During the power transistor's conduction phase, T... on The primary coil of a transformer is excited by current and is therefore also called the magnetizing coil / magnetizing winding / magnetizing inductor; while the secondary coil of a transformer can be called the demagnetizing coil / demagnetizing winding / demagnetizing inductor, which is used during the turn-off phase T of the power transistor. off An induced electromotive force is generated, which in turn produces a demagnetizing current to release energy. This demagnetizing current demagnetizes the transformer core, completely restoring the transformer's magnetic flux, and gradually decreases during this process. The demagnetizing time T... dem This is the time it takes for the demagnetizing current to gradually decrease from its maximum value to 0. The point at which the demagnetizing current of the secondary coil decreases to 0 is the end of the demagnetization process.

[0062] Discontinuous Current Mode (DCM): This means that the sum of the inductor's magnetization time and demagnetization time is equal to or approximately equal to the switching cycle. In other words, during the switching cycle of the power transistor, after the demagnetization ends, the primary inductance (including the primary coil) often resonates with some parasitic capacitances (i.e., alternating peaks and valleys), causing the voltage V between the first and second terminals of the power transistor to...ds Oscillations occur, therefore this period can also be called the oscillation time T. os The parasitic capacitance that resonates with the primary coil is, for example, the output parasitic capacitance Coss of the power transistor, and the resonance period T during the oscillation time. res For example, it can be represented as:

[0063]

[0064] Where Lp represents the inductance of the primary coil of the transformer.

[0065] Quasi-resonant (QR) control technology: can be used in discontinuous conduction mode, and selects the voltage V at the power transistor's terminals during the oscillation time. ds When the resonance reaches its lowest point, the power transistor is turned on, thus increasing the voltage V at the power transistor's terminals. ds Turning on the power transistor when it reaches zero voltage / low voltage can reduce the switching losses of the power transistor, improve the efficiency of the switching power supply circuit, and reduce electromagnetic interference noise.

[0066] Figure 1 This shows the terminal voltage V across the power transistor in a flyback switching power supply circuit employing conventional quasi-resonant control technology. ds A schematic diagram of the waveform change over time t. Where y is a positive integer greater than or equal to 1, i is a positive integer greater than or equal to 1, and k is a positive integer greater than i.

[0067] like Figure 1 As shown, traditional quasi-resonant control techniques typically pre-set two time parameters: the shielding time T. blk and the valley detection window time T w (Not shown). Wherein, the shielding time T... blk It is a fixed value, starting from the turn-on time of the power transistor on the primary side (e.g., t). i t k ), shielding time T blk The end time corresponds to the valley detection window time T. w The initial moment, the valley detection window time T w The end time can correspond to the next shielding time T. blk The starting moment.

[0068] During the shielding time after the power transistor is turned on, even if the terminal voltage V ds Once the oscillation begins and reaches its trough, the power transistor will not be turned on again. In other words, the power transistor will only be activated during the trough detection window T after the shielding time. w The first valley floor inside was opened up.

[0069] Based on the above analysis, if the circuit can lock onto a stable valley for conduction in steady state, then the following equation holds:

[0070]

[0071] In the above equation, V out I out These represent the output voltage and output current, respectively; n is the primary and secondary turns ratio of the transformer; η is the overall efficiency; and f is the output current. sw For the switching cycle, I pk N represents the peak value of the primary current of the transformer. f The valley index is the one that is locked. When the shielding time T... blk When the time is fixed, the above equation has no solution for some specific output loads: that is, it is impossible to find a fixed N. f This ensures that the above equation is satisfied. Therefore, under the action of negative feedback closed-loop control, the circuit will inevitably adjust the conduction valley to ensure the stability of the output voltage, causing a valley jump phenomenon. In traditional QR control, due to the shielding time T... blk The conduction valley remains unchanged; the adjustment of the peak value of the primary current I is achieved by adjusting the primary current peak value. pk It was achieved.

[0072] like Figure 1 As shown, in the y-th switching cycle, the end of the shielding time occurs before the first trough of the oscillation time, therefore the power transistor can be turned on at the first trough of this switching cycle; as the circuit operates, for example, in the y+i-th switching cycle, the end of the shielding time t i +T blk The first trough of the oscillation time may occur, therefore the power transistor will be turned on at the second trough after the oscillation begins; and in the (y+k)th switching cycle, the shielding time ends at time t. k +T blk The oscillation might occur before the first trough of the current switching cycle, causing the power transistor to turn on at the first trough after the start of the oscillation. Therefore, the power transistor might turn on at two adjacent troughs in each switching cycle, failing to achieve trough "lock-in." In other words, for the same input / output specifications, the power transistor cannot guarantee that it will always turn on at the Nth trough after the start of the oscillation. f The valley bottom was connected (N) f Even under steady-state conditions, the conduction time of a power transistor may switch back and forth between adjacent valleys, a phenomenon known as the "valley jumping" phenomenon.

[0073] Because there is a resonant cycle interval between adjacent valleys, the "skipping valleys" phenomenon will cause a significant change in the switching frequency, resulting in unstable switching frequency, audible noise, and negatively impacting the electromagnetic interference immunity of the switching power supply circuit. Furthermore, based on traditional quasi-resonant control technology, the valley position corresponding to the gradual increase in power from no-load to a certain output power is not necessarily the same as the valley conduction position corresponding to the gradual decrease in power from full load to the same output power. This can lead to different valley conduction positions for the same output power, meaning inconsistent switching frequencies at the same output power, which also hinders efficiency improvement.

[0074] This disclosure aims to propose a novel quasi-resonant control technique that adaptively determines the appropriate valley based on the current input / output specifications and turns on the power transistor at that valley, thereby achieving valley "locking." This ensures stable switching frequency under steady-state conditions with the same input / output specifications, avoiding "valley jumping" and improving electromagnetic interference immunity and overall system efficiency. Especially in applications such as fast charging for mobile phones that require switching power supply circuits to provide multiple output voltage specifications, the embodiments of this disclosure can better adapt to various input / output specifications, ensuring efficiency while maintaining the same switching frequency for the input / output specifications.

[0075] This invention can be presented in various forms. The following will describe some examples of this disclosure using a flyback architecture switching power supply circuit as an example.

[0076] Figure 2 A schematic diagram of the switching power supply circuit according to an embodiment of the present disclosure is shown.

[0077] like Figure 2 As shown, the switching power supply circuit 10 includes: a rectifier bridge BD0, a power transistor M0, a drive controller 100, a transformer (including at least the primary coil Lp on the primary side and the secondary coil Ls on the secondary side), and a first sampling resistor R. cs1 And a freewheeling diode D0. In addition, the switching power supply circuit 10 may also include an input capacitor Cin and an output capacitor Cout. The power transistor M0, the transformer, and the freewheeling diode can also be considered as included in the power converter of the switching power supply circuit, which is used to convert the input voltage V provided by the rectifier bridge into voltage V. in Converted to output voltage V out and the output current I acting on the load out .

[0078] The input terminal of rectifier bridge BD0 receives the AC input signal V. ac The positive output terminal provides the input voltage V. in The negative output terminal is grounded. The input capacitor Cin is connected between the positive and negative output terminals of the rectifier bridge BD0, and can be used to regulate the input voltage V.in Filtering is performed. An output voltage V is provided between the first and second output terminals of the switching power supply circuit 10. out To the load connected between the first and second output terminals (as shown in the figure, represented by impedance Z) load (Indicates the load) Power supply. The output capacitor Cout is connected between the first output terminal and the second output terminal of the switching power supply circuit 10, and the first output terminal of the switching power supply circuit 10 is connected to the cathode of the freewheeling diode D0, and the second output terminal is connected to the anode of the freewheeling diode D0 through the secondary coil Ls.

[0079] As mentioned above, in addition to achieving electrical isolation between the primary and secondary sides, transformers also serve to store and release energy.

[0080] The first terminal of power transistor M0 is connected to the positive output terminal of rectifier bridge BD0 via primary coil Lp, and the second terminal is connected via the first sampling resistor R. cs1 Connected to ground, thus power transistor M0 is connected to the first sampling resistor R. cs1 The connection node provides the sampling voltage V cs Sampling voltage V cs Characterizing the current flowing through power transistor M0, relative to the sampled voltage V cs Peak sampling can obtain the peak sampling voltage V, which represents the peak current flowing through the power transistor M0. cs(peak) Therefore, the sampling voltage V cs It can also be used to calculate the peak current I of the primary loop. pk and the output current I of the secondary circuit out .

[0081] As an example, the power transistor M0 is, for example, a field-effect transistor (FET), whose first terminal and second terminal are, for example, the drain and the source, respectively, and whose control terminal is, for example, the gate. The terminal voltage of the power transistor described in this disclosure is, for example, the drain-source voltage V. ds In some embodiments, the power transistor M0 may be a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0082] The control terminal of power transistor M0 receives the switching control signal V provided by drive controller 100. ctl Switch control signal V ctl Typically, it has a pulse width modulation (PWM) waveform, whose level state switches back and forth between high and low levels, causing the power transistor M0 to switch on and off in response to the switching control signal V. ctlUnder the action of [the transformer], it is alternately turned on and off. During the on-phase of power transistor M0, the transformer is [operated] under the input voltage V. in Energy is stored under the action of the current, which flows in series through the primary coil Lp, the power transistor M0, and the first sampling resistor R. cs1 At this time, the voltage across the power transistor M0 (terminals 1 and 2) is approximately 0; while during the turn-off phase of the power transistor M0, the transformer releases energy to the secondary circuit containing the load through the freewheeling diode D0, thereby ensuring the output voltage V. out The voltage value is maintained within a certain range.

[0083] In the embodiments disclosed herein, such as Figure 2 As shown, the switching power supply circuit 10 also includes a sampling unit 200 and a valley-locking controller 300. The sampling unit 200 is used to obtain multiple sampling signals, each representing the input voltage V. in Output voltage V out and the secondary side output current I out The valley bottom locking controller 300 is electrically connected to the sampling unit 200 to receive each sampling signal and generate a valley bottom number N based on these sampling signals. f The valley bottom indication signal causes the drive controller 100 to register the Nth valley after the start of oscillation. f The power transistor M0 is turned on at the bottom of the valley, and the adapter is numbered N at the bottom of the valley. f The valley number corresponding to the valley that is most beneficial to the overall machine efficiency is selected. Here, N f The corresponding decimal value is a natural number greater than or equal to 1.

[0084] In order to in the Nth f At each valley bottom, the power transistor M0 is turned on. The drive controller 100 may include, for example, a valley bottom counter and a turn-on control unit. The valley bottom counter is used to count the valleys that appear after the oscillation begins to obtain a valley bottom count value. The turn-on control unit activates the power transistor M0 when the valley bottom count value equals the corresponding valley number N. f A fixed delay T at or after the corresponding value delay At the end of the cycle, power transistor M0 is turned on and the valley count value is reset to zero. Fixed delay T delay For example, equal to 1 / 4 of the resonance period T res .

[0085] Figure 3 A schematic diagram of a sampling unit and valley bottom locking controller according to an embodiment of the present disclosure is shown. Figure 3 The sampling unit 200 and valley bottom locking controller 300 shown are, for example, applied to... Figure 2 The switching power supply circuit 10 shown can also be applied to other switching power supply circuits with quasi-resonant control technology.

[0086] As an example, such as Figure 2 and 3 As shown, the transformer in the switching power supply circuit 10 may also include an auxiliary coil La, so the sampling unit 200 can use the auxiliary coil La to obtain each sampling signal by primary-side sampling.

[0087] For example, the sampling unit 200 includes a first voltage divider structure, which includes a first resistor Ra1 and a second resistor Ra2 connected in series between the two ends (positive and negative ends) of the auxiliary coil La. The negative end of the auxiliary coil La is grounded, so that the first resistor Ra1 and the second resistor Ra2 divide the voltage across the auxiliary coil La. An auxiliary voltage divider signal V is provided at the intermediate node where the first resistor Ra1 and the second resistor Ra2 are connected. dem The auxiliary voltage divider signal V dem It can be used to derive the input voltage V in Output voltage V out and output current I out .

[0088] Figure 4 This diagram illustrates the waveform of the auxiliary voltage divider signal changing over time in an embodiment of the present disclosure.

[0089] During the conduction time T of power transistor M0 on Inside, such as Figure 4 As shown, since the potential across the primary coil Lp is equal to the input voltage V in Therefore, the voltage across the auxiliary coil La is equal to Where Np and Na are the number of turns in the primary and auxiliary windings of the transformer, respectively, V can be sampled during the conduction period of M0. dem The voltage obtained at this time can characterize the magnitude of the output voltage.

[0090] At the moment the power transistor M0 is turned off, the secondary coil Ls begins to generate a demagnetizing current, and the voltage across the auxiliary coil La rises instantaneously. At this time, the auxiliary voltage divider signal V... dem It rises to the maximum value within that switching cycle.

[0091] During demagnetization time T dem Inside, the auxiliary coil La gradually releases energy, assisting in voltage division V. dem The voltage gradually decreases and begins to oscillate at the end of demagnetization. Therefore, the sampling unit 200 can further adjust the voltage based on the auxiliary voltage divider signal V. dem Obtain demagnetization indication signal S dem The demagnetization indication signal S dem During demagnetization time T dem The system is in a first-level state (e.g., high level) during the internal time and a second-level state (e.g., low level) during the non-demagnetization period. This is due to the output current I... outIt is mainly generated by the demagnetization process, therefore the demagnetization indication signal S is used. dem Relative to the switching period T sw Demagnetization duty cycle D dem The output current I can be calculated. out .

[0092] During the oscillation time T os Internal auxiliary voltage divider signal V dem With the terminal voltage V of power transistor M0 ds When oscillation occurs, the valley bottom locking controller 300 calculates the appropriate valley bottom number N based on the sampling signals provided by the sampling unit 200. f (For example, corresponding to decimal values ​​1, 2, 3, 4...), then under steady-state conditions where the input voltage, output voltage, and output current remain constant, the drive controller 100 will, on the Nth day after the start of each oscillation... f The bottom of the valley or the Nth valley f A fixed delay T after the bottom delay At the end, the power transistor M0 is turned on to achieve valley locking in steady state. That is, for the same input and output specifications, the power transistor will be turned on when triggered by the same numbered valley, preventing the "valley jumping" phenomenon and improving the efficiency for the same input and output specifications.

[0093] In some examples, such as Figure 3 As shown, the sampling unit 200 may include an output current sampling module 220, used to sample the current based on the auxiliary voltage divider signal V. dem and sampling voltage V cs Generate the first sampled signal V io(fb) The first sampled signal V io(fb) It can characterize the output current I on the secondary side out .

[0094] Figure 5 A schematic diagram of the structure of an exemplary output current sampling module 220 according to an embodiment of the present disclosure is shown. Figure 5 The output current sampling module 220 shown can be applied to Figure 3 and / or Figure 2 The sampling unit 200 shown is used to provide a characterizing output current I to the valley locking controller 300. out The first sampled signal V io(fb) .

[0095] like Figure 5 As shown, the output current sampling module 220 may include a peak sampling and holding circuit 221, a demagnetizing duty cycle extraction circuit 222, a multiplier 223, and an output circuit 224.

[0096] Among them, the peak sample-and-hold circuit 221 samples the voltage V.cs Peak sampling is performed to obtain the peak sampling voltage V. cs(peak) V cs(peak) It can characterize the peak current I flowing through the power transistor. pk Peak sampling voltage V cs(peak) With peak current I pk The relationship can be expressed as:

[0097] V cs(peak) =I pk *R cs1 (2)

[0098] For the flyback architecture switching power supply circuit 10, when the switching power supply circuit 10 operates in discontinuous conduction mode, the output current I... out It can be represented as:

[0099]

[0100] In equation (3), N p N s T represents the number of turns in the primary coil Lp and the secondary coil Ls of the transformer, respectively, and is a constant. dem T represents the demagnetization time of a transformer. sw Characterizing the switching cycle of power transistor M0, such as Figure 4 As shown.

[0101] Figure 5 The demagnetizing duty cycle extraction circuit 222 shown above extracts the demagnetizing duty cycle based on the auxiliary voltage divider signal V. dem Obtain the demagnetization duty cycle D dem The calculation formula is, for example, the following formula (4):

[0102]

[0103] In some examples, the demagnetization duty cycle extraction circuit 222 can, for example, first extract the auxiliary voltage divider signal V. dem Obtain demagnetization indication signal S dem (like Figure 4 (As shown), then detect the demagnetization duty cycle D based on the demagnetization indicator signal. dem .

[0104] Figure 5 The multiplier 223 shown is electrically connected to the peak sample-and-hold circuit 221 and the demagnetizing duty cycle extraction circuit 222, respectively, and is based on the peak sampling voltage V provided by the peak sample-and-hold circuit 221. cs(peak) The demagnetizing duty cycle D provided by the demagnetizing duty cycle extraction circuit 222 dem The product of the peak sampling voltage and the demagnetization duty cycle, V, is calculated. io(cal) :

[0105] Vio(cal) =D dem *V cs(peak) (5)

[0106] Combining equations (2), (3), (4), and (5), we obtain:

[0107]

[0108] In the above formula, N p N s and R cs1 Both are constants, therefore we know Figure 3 The product result V of multiplier 223 io(cal) With output current I out The relationship is directly proportional, with the proportionality coefficient (preset coefficient) being directly proportional to the turns ratio between the primary and secondary coils and inversely proportional to the first sampling resistor R. cs1 The resistance value.

[0109] In some optional examples, in order to filter out the superposition on the product result V io(cal) To reduce noise and glitches, the output circuit 224 can adjust the product result V. io(cal) Perform low-pass filtering to obtain the filtered result V. io(filter) The first sampling signal V provided by the output circuit 224 io(fb) The product result V can be selected from one of the following: io(cal) Filtering result V io(filter) The product of the result of multiplication and the result of filtering, plus a preset coefficient, is used to determine the first sampled signal V. io(fb) It can characterize the output current I out .

[0110] In some examples, such as Figure 3 As shown, the sampling unit 200 may include an output voltage sampling module 230, used to sample the output voltage based on the auxiliary voltage divider signal V. dem Generate the second sampled signal V out(fb) The second sampled signal V out(fb) It can characterize the output voltage V out .

[0111] When using the transformer primary-side sampling method, the output voltage V cannot be directly sampled. out The voltage value can be obtained, therefore the voltage of the auxiliary coil La at the end of demagnetization can be sampled, and this voltage can be used to characterize the output voltage V. out .

[0112] For example, in the demagnetization indication signal S dem Under timing control, the output voltage sampling module 230 can sample the auxiliary voltage divider signal V when the auxiliary coil La is demagnetized.dem Sample and hold are performed to obtain the second sampled signal V. out(fb) The second sampled signal V out(fb) With output voltage V out The relationship between them can be expressed as:

[0113]

[0114] Where, N a This indicates the number of turns in the auxiliary coil La. Since N... a N s R a1 R a2 Both are constants, so the sampled voltage value V out(fb) With output voltage V out It is directly proportional. Therefore, the second sampling signal V provided by the output voltage sampling module 230 out(fb) It can characterize the output voltage V out The voltage value.

[0115] In some examples, such as Figure 3 As shown, the sampling unit 200 may include an input voltage sampling module 240, used to generate a characterization of the input voltage V. in The third sampled signal V in(fb) .

[0116] The input voltage sampling module 240 can use various methods to sample the input voltage V. in Perform sampling.

[0117] For example, the input voltage sampling module 240 can be directly connected to the positive output terminal of the rectifier bridge BD0 to facilitate the sampling of the input voltage V. in The third sampled signal V is obtained after voltage division by resistors. in(fb) .

[0118] For example, in the switch control signal V ctl Under timing control, the input voltage sampling module 240 can sample the auxiliary voltage divider signal V during the conduction phase of the power transistor M0. dem Sampling is performed to obtain the third sampled signal V. in(fb) The third sampled signal V in(fb) With input voltage V in The relationship is:

[0119]

[0120] From equation (8), it can be seen that, since N a N p R a1 R a2 All are constants, and the third sampled signal V is obtained by sampling.in(fb) The voltage value and the input voltage V in They are directly proportional.

[0121] As can be seen from the above, the input voltage V can be obtained by using the primary-side sampling method of the transformer. in Output voltage V out and output current I out The sampled signal.

[0122] Furthermore, such as Figure 3 As shown, the first sampled signal V characterizes the output current. io(fb) The second sampled signal V, representing the output voltage. out(fb) and the third sampled signal V representing the input voltage in(fb) The sampled unit 200 inputs to the valley bottom locking controller 300. The valley bottom locking controller 300 performs logical calculations based on the sampled signals provided by the sampled unit 200 to generate a valley bottom number N that represents the valley bottom. f The valley bottom indicator signal.

[0123] Valley bottom locking controller 300 can calculate and generate the appropriate valley bottom number N using various methods. f For example, the valley bottom locking controller 300 can determine the adaptation switching period T based on the values ​​of each sampled signal provided by the sampling unit 200. sw(opt) And according to the adaptation switching period T sw(opt) Determine the appropriate valley number N f This allows the power transistor to be matched to the valley number N. f The switching period when the corresponding valley is activated is equal to or close to the matching switching period T. sw(opt) This facilitates achieving the highest overall efficiency under current input / output specifications and enables adaptive response to input voltage, output voltage, and output current.

[0124] As an example, the valley-locking controller 300 may include a function construction unit and an adaptation unit. The function construction unit is used to construct a corresponding down-frequency function based on one or more sampled signals provided by the sampling unit 200, where the dependent variable of the down-frequency function represents the adaptation switching period T. sw(opt) The independent variable is any one of the input voltage, output voltage, and output current. The sampled signals used to construct the frequency reduction function represent one or more of the input voltage, output voltage, and output current. Based on the sampled signals corresponding to the independent variables of the frequency reduction function provided by the sampling unit 200 and the frequency reduction function obtained by the function construction unit, the adaptation unit determines the function value of the frequency reduction function in order to obtain the adaptation switching period T that is most beneficial to the overall efficiency under the current input and output specifications. sw(opt) And select the corresponding switching period T. sw(opt) Matching fit valley number N f.

[0125] Function building blocks can be implemented using either digital or analog circuits.

[0126] The valley-locking controller 300 can determine the appropriate valley number N under steady-state conditions with the current input / output specifications. f Furthermore, it can readjust the down-frequency function based on each sampled signal in steady state after the input / output specifications have changed, thereby generating an adaptive valley number N that matches the changed input / output specifications. f This enables adaptive control that locks in at the valley floor.

[0127] Figures 6a to 6c Schematic structural block diagrams of valley bottom locking controllers according to embodiments of the present disclosure are shown respectively.

[0128] As an example, such as Figure 6a As shown, the valley bottom locking controller 300 includes a function construction unit 310 and an adaptation unit 320.

[0129] The function construction unit 310 is configured to: based on the circuit parameters of the switching power supply circuit 10 and the second sampling signal V provided by the sampling unit 200 out(fb) and the third sampled signal V in(fb) The value of the frequency reduction function g1 is used to construct the frequency reduction function g1, and the independent variable of the frequency reduction function g1 is the output current I. out The dependent variable is the adaptation switch period T. sw(opt) .

[0130] For example, the function construction unit 310 can be based on the third sampled signal V representing the input voltage. in(fb) and the second sampled signal V representing the output voltage out(fb) Determine one or more coefficients of the frequency reduction function g1 such that the frequency reduction function g1 varies with the output current I. out The variation curve can be used to determine the adaptation switch period T. sw(opt) In this example, the down-frequency function g1 and the adaptation switching period T sw(opt) It can be represented as:

[0131] T sw(opt) =g1(V in(fb) V out(fb) ,I out (9)

[0132] Equation (9) describes: when the input voltage V in With output voltage V out Under steady-state conditions (i.e., when sampling can be performed stably), different output currents I out Corresponding adapter switching period T sw(opt)It can be calculated from the frequency reduction function g1. The specific expression of the frequency reduction function g1 should be determined according to the actual peripheral design of the valley locking controller 300. Here, it is directly described by the function symbol g1, which does not affect the understanding of the present invention.

[0133] Figure 7 This diagram illustrates the curves of the adaptive switching frequency versus output current calculated by the function construction unit of this embodiment under different input and output voltages. Wherein, I out(max) This indicates the maximum allowable output current of the switching power supply circuit 10, and the compatible switching frequency F. sw(opt) =1 / T sw(opt) .

[0134] like Figure 7 As shown, at the input voltage V in =V in1 Output voltage V out =V out1 In this case, function construction unit 310 determines the corresponding frequency reduction function g1 (e.g., Figure 7 The solid line curve G11 represents the adaptive switching frequency F under this condition. sw(opt) With output current I out The change, that is, the change in the output current I of the switching power supply circuit 10. out Given a specific frequency, the corresponding adaptive switching frequency F can be determined based on the frequency reduction function g1 and / or curve G11. sw(opt) .

[0135] And at the input voltage V in =V in2 Output voltage V out =V out2 In this case, function construction unit 310 determines the corresponding frequency reduction function g1 (e.g., Figure 7 The curve G12 (shown by the dashed line) represents the adaptive switching frequency F under this condition. sw(opt) With output current I out The change, that is, the change in the output current I of the switching power supply circuit 10. out Given a specific frequency, the corresponding adaptive switching frequency F can be determined based on the frequency reduction function g1 and / or curve G12. sw(opt) .

[0136] Depend on Figure 7 As can be seen, based on the aforementioned frequency reduction function g1, the valley-locking controller 300 can adjust the input voltage V according to the input voltage V. in Output voltage V out and output current I out Adaptively determine and adjust the appropriate switching frequency F of power transistor M0 sw(opt) The switching frequency F of the switching power supply circuit 10sw The closer it gets to the suitable switching frequency F sw(opt) The higher the efficiency, the better.

[0137] As an example, the adapter unit 320 uses the remaining first sampled signal V provided by the sampling unit 200. io(fb) (characterizing the output current I) out The optimal valley is selected from the frequency reduction curve determined by equation (9) for locking. The optimal valley refers to the valley among which the switching period T after valley locking control can be guaranteed (e.g., the first to m valleys after the start of oscillation, where m is a natural number greater than or equal to 2). sw The adaptation switching period T determined by equation (9) sw(opt) The closest valley bottom, the best-fit valley bottom, is numbered as the best-fit valley bottom number N. f (Greater than / equal to 1, and less than / equal to m), this fits the valley number N. f For example, it can be determined by the following constraint:

[0138]

[0139] In the above formula, L p This represents the inductance of the primary coil of the transformer; n = N p / N s This indicates the turns ratio between the primary and secondary coils of a transformer; I pk T represents the peak value of the primary current; res This indicates the resonance period after demagnetization has ended. C oss The capacitance of the negative terminal of the primary coil on the primary side to ground (e.g., the output capacitance of the power transistor M0).

[0140] The appropriate valley number N can be obtained from equation (10). f The value of the adaptive switching period T is determined by the frequency reduction function g1 of the current input / output specification. sw(opt) The duration is limited to the Nth time. f The switching cycle corresponding to the Nth valley is related to the (N)th valley. f +1) between the switching cycles corresponding to the valleys. In some alternative embodiments, the adaptive switching cycle T determined by the down-frequency function g1 can also be... sw(opt) The duration is limited to the Nth ( f -1) The switching cycle corresponding to the Nth valley bottom and the Nth f Between the switching cycles corresponding to each valley bottom.

[0141] Adapted to valley bottom number N fThe valley number that needs to be locked is indicated, so that the drive controller 100 can adjust the valley indication signal (representing the valley number N) provided by the valley locking controller 300. f Valley locking is performed so that the power transistor M0 is turned on at the most suitable valley, thereby stabilizing the switching frequency of the switching power supply circuit 10 and avoiding valley frequency jumping.

[0142] Figure 8 The diagram shows the switching frequency and the adaptive switching frequency of the switching power supply circuit according to an embodiment of the present disclosure as a function of the output current.

[0143] from Figure 8 It can be seen that after valley bottom locking is performed, the switching frequency F of the switching power supply circuit 10 is... sw In the corresponding adaptive switching frequency F sw(opt) The nearby changing frequency F sw The curve showing the change in output current varies near the corresponding frequency reduction curve. The switching frequency F... sw with I out Relatedly, regardless of whether the output power is in the rising or falling phase, the same input and output specifications correspond to the same switching frequency, realizing valley locking for each input and output specification. While reducing switching power consumption by using quasi-resonant control technology, efficiency is improved, the "valley jumping" phenomenon is avoided, and the impact of electromagnetic interference is reduced.

[0144] As mentioned above, the third sampled signal V, which represents the input voltage, in(fb) The second sampled signal V, representing the output voltage. out(fb) and the first sampled signal V representing the output current io(fb) They are independent and equivalent, and can be converted into each other. Therefore, as another example, the down-frequency function used to select the appropriate valley number can not only be expressed as the down-frequency function g1 described by equation (9), but also as the function derived from the third sampled signal V. in(fb) and the first sampled signal V io(fb) The constructed frequency reduction function g2 is:

[0145] T sw(opt) =g2(V in(fb) V io(fb) V out (11)

[0146] In equation (11), V out As the independent variable, the adaptation switching period T sw(opt) As the dependent variable, the third sampled signal V in(fb) and the first sampled signal V io(fb) The value of is used to determine the corresponding coefficients in the frequency reduction function g2. Equation (11) describes: when the input voltage Vin With output current I out Under steady-state conditions (i.e., when sampling can be performed stably), different output voltages V out Corresponding adapter switching period T sw(opt) It can be calculated from the frequency reduction function g2. The specific expression of the frequency reduction function g2 should be determined according to the actual peripheral design of the valley locking controller 300. Here, it is directly described by the function symbol g2, which does not affect the understanding of the present invention.

[0147] Combination Figure 6b The function construction unit 310 constructs the signal based on the circuit parameters of the switching power supply circuit 10 and the third sampling signal V provided by the sampling unit 200. in(fb) and the first sampled signal V io(fb) The value of V is used to construct the frequency reduction function g2, and thus the frequency reduction function g2 varies with the output voltage V. out The variation curve can be used to determine the adaptation switch period T. sw(opt) .

[0148] The adapter unit 320 uses the remaining second sampling signal V provided by the sampling unit 200. out(fb) (characterizing the output voltage V) out The frequency reduction curve and / or frequency reduction function g2 determined by equation (11) can be used to select the most suitable valley for locking: In each valley, if the corresponding switching period T sw More closely approximating the current output voltage V out (from the second sampling signal V) out(fb) Characterization) The adaptive switching period T determined based on the frequency reduction function g2 sw(opt) If the valley is the most suitable valley, then that valley is the one that best fits the market. The best-fit valley is the one with the corresponding switching period T among all the valleys (for example, the first to m valleys after the start of oscillation, where m is a natural number greater than or equal to 2). sw The closest matching switching period T determined by the down-frequency function g2 sw(opt) The valley floor. The most suitable valley floor corresponds to the number N. f (Greater than / equal to 1, and less than / equal to m), this fits the valley number N. f The value can be selected, for example, by the following formula:

[0149]

[0150] The appropriate valley number N can be obtained from equation (12). f The value of the adaptive switching period T is determined by the frequency reduction function g2 to make the current input / output specifications decrease. sw(opt) The duration is limited to the Nth time. f The switching cycle corresponding to the Nth valley is related to the (N)th valley. f+1) between the switching cycles corresponding to the valleys. In some alternative embodiments, the adaptive switching cycle T determined by the down-frequency function g2 can also be... sw(opt) The duration is limited to the Nth ( f -1) The switching cycle corresponding to the Nth valley bottom and the Nth f Between the switching cycles corresponding to each valley bottom.

[0151] Adapted to valley bottom number N f The valley number that needs to be locked is indicated, so that the drive controller 100 can adjust the valley indication signal (representing the valley number N) provided by the valley locking controller 300. f Valley locking is performed so that the power transistor M0 is turned on at the most suitable valley, thereby stabilizing the switching frequency of the switching power supply circuit 10 and avoiding valley frequency jumping.

[0152] As yet another example, the down-frequency function can also be expressed as a function of the second sampled signal V, which characterizes the output voltage. out(fb) and the first sampled signal V representing the output current io(fb) The defined frequency reduction function g3 is:

[0153] T sw(opt) =g3(V out(fb) V io(fb) V in (13)

[0154] In equation (13), V in It is used as the independent variable to adapt to the switching period T. sw(opt) As the dependent variable, the second sampled signal V out(fb) and the first sampled signal V io(fb) The value of is used to determine the corresponding coefficients in the frequency reduction function g3. Equation (13) describes: when the output current I out With output voltage V out Under steady-state conditions (i.e., conditions that can be stably sampled), different input voltages V in Corresponding adapter switching period T sw(opt) It can be calculated from the frequency reduction function g3. The specific expression of the frequency reduction function g3 should be determined according to the actual peripheral design of the valley locking controller 300. Here, it is directly described by the function symbol g3, which does not affect the understanding of the present invention.

[0155] Combination Figure 6c The function construction unit 310 constructs the signal based on the circuit parameters of the switching power supply circuit 10 and the first sampling signal V provided by the sampling unit 200. io(fb) Second sampled signal V out(fb) The value of V is used to construct the frequency reduction function g3, and thus the frequency reduction function g3 varies with the input voltage V. inThe variation curve can be used to determine the adaptation switch period T. sw(opt) .

[0156] The adapter unit 320 uses the remaining third sampling signal V provided by the sampling unit 200. in(fb) (characterizing the output voltage V) in The frequency reduction curve and / or frequency reduction function g3 determined by equation (13) can be used to select the most suitable valley for locking: In each valley, if the corresponding switching period T sw Closer to the current input voltage V in (from the third sampled signal V) in(fb) Characterization) The adaptive switching period T determined based on the frequency reduction function g3 sw(opt) If the valley is the most suitable valley, then that valley is the one that best fits the market. The best-fit valley is the one with the corresponding switching period T among all the valleys (for example, the first to m valleys after the start of oscillation, where m is a natural number greater than or equal to 2). sw The closest matching switching period T determined by the down-frequency function g3 sw(opt) The valley floor. The most suitable valley floor corresponds to the number N. f (Greater than / equal to 1, and less than / equal to m), this fits the valley number N. f The value can be selected, for example, by the following formula:

[0157]

[0158] The appropriate valley number N can be obtained from equation (14). f The value of the adaptive switching period T is determined by the frequency reduction function g3 to reduce the current input / output specifications. sw(opt) The duration is limited to the Nth time. f The switching cycle corresponding to the Nth valley is related to the (N)th valley. f +1) between the switching cycles corresponding to the valleys. In some alternative embodiments, the adaptive switching cycle T determined by the down-frequency function g3 can also be... sw(opt) The duration is limited to the Nth ( f -1) The switching cycle corresponding to the Nth valley bottom and the Nth f Between the switching cycles corresponding to each valley bottom.

[0159] Adapted to valley bottom number N f The valley number that needs to be locked is indicated, so that the drive controller 100 can adjust the valley indication signal (representing the valley number N) provided by the valley locking controller 300. f Valley locking is performed so that the power transistor M0 is turned on at the most suitable valley, thereby stabilizing the switching frequency of the switching power supply circuit 10 and avoiding valley frequency jumping.

[0160] As can be seen from the above embodiments, the embodiments of this disclosure characterize the sampling signals V representing the input voltage, output voltage, and output current. in(fb) V out(fb) and V io(fb) As the input signal of the valley locking control circuit 300, the valley locking controller 300 can adaptively select the valley that best matches the current input and output specifications, and then drive the controller 100 to turn on the power transistor at the most suitable valley. Thus, regardless of whether the output power is in the rising or falling phase, the same input and output specifications correspond to the same switching frequency, realizing valley locking and adaptation for each input and output specification. While reducing switching power consumption by using quasi-resonant control technology, it improves efficiency, avoids the "valley jumping" phenomenon, and reduces the impact of electromagnetic interference.

[0161] The above embodiments are only some possible embodiments of this disclosure, that is, the embodiments of this disclosure are not limited thereto.

[0162] For example, Figure 9 This diagram illustrates yet another structural schematic of the sampling unit and valley locking controller according to an embodiment of the present disclosure. Figure 9 The sampling unit 200 and valley bottom locking controller 300 shown are, for example, applied to... Figure 2 The switching power supply circuit 10 shown can also be applied to other switching power supply circuits with quasi-resonant control technology.

[0163] As an example, such as Figure 2 and 9 As shown, the transformer in the switching power supply circuit 10 may not include an auxiliary coil. Accordingly, the sampling unit 200 may use secondary-side sampling to obtain each sampling signal.

[0164] In some examples, such as Figure 9 As shown, the sampling unit 200 includes an output current sampling module 220, used to generate a characterizing output current I. out The first sampled signal V io(fb) .

[0165] The output current sampling module 220 may include, for example, a second sampling resistor R connected in series between the second output terminal of the switching power supply circuit 10 and the output capacitor Cout. cs2 Output current I out Flow through the second sampling resistor R cs2 Therefore, the second sampling resistor R cs2 One end connected to the second output terminal of the switching power supply circuit 10 can provide a characterization of the output current I. out The first sampled signal V io(fb) .

[0166] In some examples, such as Figure 9 As shown, the sampling unit 200 may include an output voltage sampling module 230, used to generate a characterizing output voltage V. out The second sampled signal V out(fb) .

[0167] The output voltage sampling module 230 can be implemented, for example, by a second voltage divider structure, which may include a third resistor Rb1 and a fourth resistor Rb2 connected in series between the first output terminal of the switching power supply circuit 10 and ground, so that the third resistor Rb1 and the fourth resistor Rb2 affect the output voltage V. out Voltage division is performed, and the second sampling signal V is provided at the intermediate node where the third resistor Rb1 and the fourth resistor Rb2 are connected. out(fb) .

[0168] In some examples, such as Figure 9 As shown, the sampling unit 200 may include an input voltage sampling module 240, used to generate a characterization of the input voltage V. in The third sampled signal V in(fb) .

[0169] The input voltage sampling module 240 can use various methods to sample the input voltage V. in Perform sampling.

[0170] For example, the input voltage sampling module 240 can be implemented by sampling circuit 241 and third voltage divider structure.

[0171] The third voltage divider structure includes anode connected in series with the freewheeling diode D0 (providing the secondary node voltage V). D0 The fifth resistor Rd1 and the sixth resistor Rd2 are connected to the ground, and thus the fifth resistor Rd1 and the sixth resistor Rd2 affect the secondary node voltage V. D0 Voltage division is performed, with the secondary voltage divider signal V provided at the intermediate node connecting the fifth resistor Rd1 and the sixth resistor Rd2. d1 .

[0172] In the switch control signal V ctl Under the timing control, the sampling circuit 241 can divide the secondary voltage signal V during the conduction phase of the power transistor M0. d1 Sampling is performed to obtain a characterization of the input voltage V. in The third sampled signal V in(fb) .

[0173] Based on the relationship characteristics between the primary and secondary coils of a transformer, the secondary node voltage V D0 The input voltage V can be characterized during the conduction period of the power transistor on the primary side. in Therefore, the third sampled signal V obtained during the conduction phase of the power transistor... in(fb) It can characterize the input voltage V on the primary side. in,Right now:

[0174]

[0175] Furthermore, similar to or the same as in the embodiments described above, the first sampling signal V characterizing the output current... io(fb) The second sampled signal V, representing the output voltage. out(fb) and the third sampled signal V representing the input voltage in(fb) The sampled unit 200 inputs to the valley bottom locking controller 300. The valley bottom locking controller 300 performs logical calculations based on the sampled signals provided by the sampled unit 200 to generate a valley bottom number N that represents the valley bottom. f The valley bottom indicator signal.

[0176] The valley bottom locking controller 300 can calculate and generate the appropriate valley bottom number N using the methods described above. f And provide the valley number N that represents the adaptation. f The valley bottom indicator signal is sent to the drive controller 100, which will not be described in detail here.

[0177] Compared to Figure 3 The illustrated embodiment employs a secondary-side sampling method to obtain the first sampled signal V. io(fb) The output current sampling module 220 and the method for obtaining the second sampling signal V out(fb) The output voltage sampling module 230 does not need to sample signals at specific stages under timing control, thus saving timing circuitry and eliminating the need for additional auxiliary coils, resulting in a simpler structure and lower cost and design difficulty compared to other modules.

[0178] It should be noted that, although Figure 9 The sampling unit 200 shown uses secondary-side sampling to obtain the sampled signals of input voltage, output voltage, and output current. However, given that the switching power supply circuit 10 includes an auxiliary coil, Figure 9 One or more of the output current sampling module 220, output voltage sampling module 230, and input voltage sampling module 240 shown can also be applied to Figure 3 In the illustrated embodiment, the sampling unit 200 can obtain the sampled signals of the input voltage, output voltage, and output current by combining primary-side sampling and secondary-side sampling.

[0179] In summary, the embodiments of this disclosure adaptively select the valley that best matches the current input and output specifications based on the sampling signals characterizing the input voltage, output voltage, and output current. Then, the power transistor is turned on at the best-matched valley. Thus, regardless of whether the output power is in the rising or falling phase, the same input and output specifications correspond to the same switching frequency. This achieves self-adaptation and valley locking for each input and output specification. While reducing switching power consumption using quasi-resonant control technology, it also improves efficiency, avoids the "valley jumping" phenomenon, and reduces the impact of electromagnetic interference.

[0180] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0181] As described above, these embodiments of the present invention do not exhaustively cover all details, nor do they limit the invention to the specific embodiments described. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A control circuit for a power converter, characterized in that, include: The sampling unit is used to sample the input voltage, output voltage, and output current of the power converter to obtain multiple sampling signals; A valley locking controller is electrically connected to the sampling unit and determines the adaptation switching period based on the values ​​of the multiple sampling signals. It also determines the corresponding adaptation valley number Nf based on the adaptation switching period, such that the duration of the adaptation switching period is limited between the switching period corresponding to the Nf-th valley and the switching period corresponding to the Nf+1-th valley, or the duration of the adaptation switching period is limited between the switching period corresponding to the Nf-1-th valley and the switching period corresponding to the Nf-th valley, so as to adaptively select the most suitable valley that matches the current input and output specifications. as well as The drive controller is electrically connected to the valley locking controller to obtain the optimal valley, so as to turn on the power transistor of the power converter at the optimal valley after the demagnetization of the power converter is completed. The optimal valley is represented by the valley number, where Nf is a natural number greater than 0.

2. The control circuit according to claim 1, characterized in that, The valley-locking controller includes: a function construction unit, which constructs a down-frequency function based on one or more of the plurality of sampled signals, wherein the independent variable of the down-frequency function corresponds to one of the plurality of sampled signals, and the dependent variable corresponds to an adaptive switching cycle that is beneficial to the efficiency of the power converter; and The adaptation unit determines the adaptation switching period based on the value of the sampled signal corresponding to the down-frequency function and its independent variable, and determines the corresponding adaptation valley number N based on the adaptation switching period. f So that the duration of the adapter switch cycle is limited to the Nth cycle. f The switching cycle corresponding to the Nth valley is related to the Nth valley. f Between ±1 valleys corresponding to the switching cycles.

3. The control circuit according to claim 2, characterized in that, The function construction unit establishes the frequency reduction function based on the sampled signal representing the output voltage and the sampled signal representing the input voltage, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal of the output current. The adapter unit substitutes the value of the sampled signal characterizing the output current into the down-frequency function to determine the adapter switching period and the adapter valley number.

4. The control circuit according to claim 2, characterized in that, The function construction unit establishes the frequency reduction function based on the sampled signal representing the input voltage and the sampled signal representing the output current, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal of the output voltage. The adapter unit substitutes the value of the sampled signal characterizing the output voltage into the down-frequency function to determine the adapter switching period and the adapter valley number.

5. The control circuit according to claim 2, characterized in that, The function construction unit establishes the frequency reduction function based on the sampled signal representing the output voltage and the sampled signal representing the output current, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal of the input voltage. The adapter unit substitutes the value of the sampled signal characterizing the input voltage into the down-frequency function to determine the adapter switching period and the adapter valley number.

6. The control circuit according to claim 2, characterized in that, The adapter unit is adapted to determine the switching cycle corresponding to each valley based on the inductance value of the primary coil of the transformer in the power converter, the turns ratio between the primary and secondary coils of the transformer, the input voltage, the output voltage, the peak current flowing through the power transistor, and the resonant period after demagnetization.

7. The control circuit according to claim 1, characterized in that, The valley bottom locking controller is also adapted to: adjust the corresponding adaptive valley bottom number according to the values ​​of the plurality of sampled signals in a steady state.

8. The control circuit according to claim 1, characterized in that, The sampling unit includes: An input voltage sampling module is used to obtain a sampling signal characterizing the input voltage; An output voltage sampling module is used to obtain a sampling signal characterizing the output voltage; and An output current sampling module is used to obtain a sampling signal characterizing the output current.

9. The control circuit according to claim 8, characterized in that, It also includes an auxiliary coil, which is coupled to the primary coil of the transformer in the power converter. The sampling unit further includes a first voltage divider structure for dividing the voltage across the auxiliary coil to obtain an auxiliary voltage divider signal, so that one or more of the input voltage sampling module, the output voltage sampling module, and the output current sampling module can obtain the corresponding sampling signal based on the auxiliary voltage divider signal.

10. The control circuit according to claim 9, characterized in that, The input voltage sampling module is suitable for: The auxiliary voltage divider signal is sampled during the conduction phase of the power transistor to obtain a sampled signal characterizing the input voltage.

11. The control circuit according to claim 9, characterized in that, The output voltage sampling module is suitable for: At the end of demagnetization, the auxiliary voltage divider signal is sampled and held to obtain a sampled signal characterizing the output voltage.

12. The control circuit according to claim 9, characterized in that, The output current sampling module is suitable for: The demagnetizing duty cycle relative to the switching cycle is obtained based on the auxiliary voltage divider signal, and a sampling signal characterizing the output current is obtained by multiplying the demagnetizing duty cycle and the peak voltage sampling value of the transformer primary current sampling resistor.

13. The control circuit according to claim 12, characterized in that, The sampling signal characterizing the output current is selected from one of the following: The product of the demagnetization duty cycle and the peak voltage sampled value of the transformer primary current sampling resistor, and the product of this product with a preset coefficient; The filtered result obtained by low-pass filtering the product result is then multiplied by a preset coefficient.

14. The control circuit according to claim 13, characterized in that, The preset coefficient is proportional to the turns ratio between the primary and secondary coils in the transformer and inversely proportional to the resistance value of the primary current sampling resistor of the transformer.

15. The control circuit according to claim 14, characterized in that, The output current sampling module includes: The voltage peak sampling and holding circuit of the transformer primary current sampling resistor performs peak sampling on the voltage at the connection node between the power transistor and the transformer primary current sampling resistor to obtain the peak sampling voltage. The demagnetizing duty cycle extraction circuit obtains the demagnetizing time based on the auxiliary voltage divider signal, and obtains the demagnetizing duty cycle based on the ratio of the demagnetizing time to the switching cycle; A multiplier is used to calculate the product of the demagnetization duty cycle and the peak sampling voltage, so as to output the product result; and The output circuit provides a sampling signal characterizing the output current based on the product result.

16. The control circuit according to claim 8, characterized in that, The input voltage sampling module is suitable for: The voltage across the secondary winding of the transformer in the power converter is divided to obtain a secondary voltage divider signal, and the secondary voltage divider signal is sampled during the conduction phase of the power transistor to obtain a sampling signal characterizing the input voltage.

17. The control circuit according to claim 8, characterized in that, The output voltage sampling module includes a second voltage divider structure. The second voltage divider structure divides the output voltage to obtain a sampling signal characterizing the output voltage.

18. The control circuit according to claim 8, characterized in that, The output current sampling module includes a second sampling resistor. The output current of the power converter flows sequentially through the load connected in series and the second sampling resistor. The connection node between the second sampling resistor and the load provides a sampling signal characterizing the output current.

19. A control method for a power converter, characterized in that, include: The input voltage, output voltage, and output current of the power converter are sampled to obtain multiple sampling signals; The adaptation switch period is determined based on the values ​​of the multiple sampled signals, and the corresponding adaptation valley number Nf is determined based on the adaptation switch period. The duration of the adaptation switch period is limited to the switch period corresponding to the Nf-th valley and the switch period corresponding to the Nf+1-th valley, or the duration of the adaptation switch period is limited to the switch period corresponding to the Nf-1-th valley and the switch period corresponding to the Nf-th valley, so as to adaptively select the best adaptation valley that matches the current input and output specifications. as well as The power transistor of the power converter is turned on at the optimal valley after the demagnetization of the power converter is completed. The optimal valley is represented by the valley number, where Nf is a natural number greater than 0.

20. The control method according to claim 19, characterized in that, The adaptation switch period is determined based on the values ​​of the multiple sampled signals, and the corresponding adaptation valley number N is determined based on the adaptation switch period. f The steps include: A frequency reduction function is constructed based on one or more of the plurality of sampled signals, wherein the independent variable of the frequency reduction function corresponds to one of the plurality of sampled signals, and the dependent variable corresponds to the adaptive switching period that is beneficial to the efficiency of the power converter; and The adaptation switch period is determined based on the value of the sampled signal corresponding to the frequency reduction function and its independent variable, and the corresponding adaptation valley number N is determined based on the adaptation switch period. f So that the duration of the adapter switch cycle is limited to the Nth cycle. f The switching cycle corresponding to the Nth valley is related to the Nth valley. f Between ±1 valleys corresponding to the switching cycles.

21. The control method according to claim 20, characterized in that, The step of constructing a frequency reduction function based on one or more of the plurality of sampled signals includes: establishing the frequency reduction function according to the sampled signal characterizing the output voltage and the sampled signal characterizing the input voltage, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal of the output current, and the value of the sampled signal of the output current is used to be substituted into the frequency reduction function to determine the adaptation switching period and the adaptation valley number.

22. The control method according to claim 20, characterized in that, The step of constructing a frequency reduction function based on one or more of the plurality of sampled signals includes: establishing the frequency reduction function according to the sampled signal characterizing the input voltage and the sampled signal characterizing the output current, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal of the output voltage, and the value of the sampled signal of the output voltage is used to be substituted into the frequency reduction function to determine the adaptation switching period and the adaptation valley number.

23. The control method according to claim 20, characterized in that, The step of constructing a frequency reduction function based on one or more of the plurality of sampled signals includes: establishing the frequency reduction function according to the sampled signal characterizing the output voltage and the sampled signal characterizing the output current, wherein the independent variable of the frequency reduction function corresponds to the value of the sampled signal of the input voltage, and the value of the sampled signal of the input voltage is used to be substituted into the frequency reduction function to determine the adaptation switching period and the adaptation valley number.

24. The control method according to claim 20, characterized in that, The step of determining the adaptation switch period based on the value of the sampled signal corresponding to the frequency reduction function and its independent variable includes: The switching cycle corresponding to each valley is determined based on the inductance value of the primary coil of the transformer in the power converter, the turns ratio between the primary and secondary coils of the transformer, the input voltage, the output voltage, the peak current flowing through the power transistor, and the resonance period after demagnetization.

25. The control method according to claim 20, characterized in that, The corresponding valley number N is determined based on the values ​​of the multiple sampled signals. f The steps also include: Under steady state, the corresponding valley number is adjusted according to the values ​​of the multiple sampled signals.

26. The control method according to claim 19, characterized in that, The steps for sampling the input voltage, output voltage, and output current of the power converter include: An auxiliary voltage divider signal is obtained based on the voltage across an auxiliary coil coupled to the primary coil of the transformer in the power converter. The auxiliary voltage divider signal is sampled during the conduction phase of the power transistor to obtain a sampled signal characterizing the input voltage; At the end of demagnetization, the auxiliary voltage divider signal is sampled and held to obtain a sampled signal characterizing the output voltage; The demagnetizing duty cycle relative to the switching cycle is obtained based on the auxiliary voltage divider signal, and a sampling signal characterizing the output current is obtained by multiplying the demagnetizing duty cycle and the peak voltage sampling value of the transformer primary current sampling resistor.

27. The control method according to claim 26, characterized in that, The sampling signal characterizing the output current is selected from one of the following: The product of the demagnetization duty cycle and the peak voltage sampled value of the transformer primary current sampling resistor, and the product of this product with a preset coefficient; The filtered result obtained by low-pass filtering the product result is then multiplied by a preset coefficient.

28. The control method according to claim 27, characterized in that, The preset coefficient is proportional to the turns ratio between the primary and secondary coils in the transformer and inversely proportional to the resistance value of the primary current sampling resistor of the transformer.

29. The control method according to claim 28, characterized in that, The steps for sampling the input voltage, output voltage, and output current of the power converter include: The voltage across the secondary winding of the transformer in the power converter is divided to obtain a secondary voltage divider signal, and the secondary voltage divider signal is sampled during the conduction phase of the power transistor to obtain a sampling signal characterizing the input voltage. The output voltage is divided to obtain a sampling signal characterizing the output voltage; The output current sampling signal is characterized by a second sampling resistor connected in series with the load, and the signal provided at the connection point between the second sampling resistor and the load.

30. A switching power supply circuit, comprising a rectifier bridge, a power converter, and a control circuit. The rectifier bridge rectifies the AC input signal to generate an input voltage, which the power converter then converts to generate an output voltage and an output current acting on the load. in, The control circuit includes: A sampling unit is used to sample the input voltage, the output voltage, and the output current to obtain multiple sampling signals; A valley-locking controller, electrically connected to the sampling unit, determines an adaptation switching period based on the values ​​of the multiple sampled signals, and determines a corresponding adaptation valley number Nf based on the adaptation switching period. The duration of the adaptation switching period is limited to the switching period corresponding to the Nf-th valley and the switching period corresponding to the (Nf+1)-th valley, or the duration of the adaptation switching period is limited to the switching period corresponding to the (Nf-1)-th valley and the switching period corresponding to the Nf-th valley, to adaptively select the most suitable valley matching the current input / output specifications; and The drive controller is electrically connected to the valley locking controller to obtain the optimal valley, so as to turn on the power transistor of the power converter at the optimal valley after the demagnetization of the power converter is completed. The optimal valley is represented by the valley number, where Nf is a natural number greater than 0.

31. A drive control method, which provides output voltage and output current to a load based on input voltage by controlling the on and off states of a power transistor in a power converter, characterized in that... The drive control method includes: The input voltage, the output voltage, and the output current are sampled to obtain multiple sampled signals; The adaptation switching period is determined based on the values ​​of the multiple sampled signals, and the corresponding adaptation valley number Nf is determined based on the adaptation switching period. The duration of the adaptation switching period is limited to the switching period corresponding to the Nf-th valley and the switching period corresponding to the (Nf+1)-th valley, or the duration of the adaptation switching period is limited to the switching period corresponding to the (Nf-1)-th valley and the switching period corresponding to the Nf-th valley, to adaptively select the best-fit valley matching the current input / output specifications; and The power transistor is turned on at the optimal valley after the power converter demagnetization is completed. The optimal valley is represented by the valley number, where Nf is a natural number greater than 0.

Images